The present invention relates to an extruded thermoplastic decorative molding especially adapted for use in automobiles and having a colored metallic appearance which substantially matches the exterior finish of the automobile body.
Functionally shaped moldings used on automobiles, for example to frame the quarter window, are conventionally made of painted metal in order to match the appearance of the moldings with the automobile body. The moldings are conventionally secured to the body by metallic clips which have a tendency to corrode during use. Also the paint coatings tend to chip during use, detracting from the appearance of the molding. Further, the paint bond often fails as the paint ages.
Many of these problems would be alleviated by a molding formed from a thermoplastic material such as polyvinyl chloride which is largely impervious to rust and corrosion due to the elements. It has been found difficult, however, to extrude the irregular shape required of such moldings and provide a uniform distribution of metallic pigment on the surface of the molding which, of course, is required in order for the molding to match the automobile body in appearance or color as required of a decorative trim. When extruding metallic pigment-containing thermoplastic material into a molding having an irregularly-shaped cross section, the die required to give the molding its irregular shape apparently causes shear forces which disturb the flow and effect the uniformity of the distribution of metallic pigment in the thermoplastic. The end results is that the molding has streaks and presents a non-uniform appearance. On the other hand, in a simple or plain extrusion, a uniform finish can be obtained because the flow of the plastic during the extrusion is relatively smooth and undisturbed resulting in a consistent and uniform distribution of the pigment in the thermoplastic. However, a plain extrusion will not provide a molding having the irregular shape required of a functional molding.
Wherefore, it is an object of the present invention to provide a decorative molding having an irregular cross section and yet presenting a surface having a uniform, colored, metallic appearance. It is another object of the present invention to provide a molding having a surface portion which substantially matches the body of an automobile and a surface portion which presents a decorative, bright chrome-like appearance. These and other objects will be apparent from the following disclosure.